XMG : eXtensible MetaGrammar

International audienceIn this article, we introduce eXtensible MetaGrammar (xmg), a framework for specifying tree-based grammars such as Feature-Based Lexicalised Tree-Adjoining Grammars (FB-LTAG) and Interaction Grammars (IG). We argue that xmg displays three features which facilitate both grammar writing and a fast prototyping of tree-based grammars. Firstly, \xmg\ is fully declarative. For instance, it permits a declarative treatment of diathesis that markedly departs from the procedural lexical rules often used to specify tree-based grammars. Secondly, the \xmg\ language has a high notational expressivity in that it supports multiple linguistic dimensions, inheritance and a sophisticated treatment of identifiers. Thirdly, xmg is extensible in that its computational architecture facilitates the extension to other linguistic formalisms. We explain how this architecture naturally supports the design of three linguistic formalisms namely, FB-LTAG, IG, and Multi-Component Tree-Adjoining Grammar (MC-TAG). We further show how it permits a straightforward integration of additional mechanisms such as linguistic and formal principles. To further illustrate the declarativity, notational expressivity and extensibility of \xmg , we describe the methodology used to specify an FB-LTAG for French augmented with a unification-based compositional semantics. This illustrates both how xmg facilitates the modelling of the tree fragment hierarchies required to specify tree-based grammars and of a syntax/semantics interface between semantic representations and syntactic trees. Finally, we briefly report on several grammars for French, English and German that were implemented using \xmg\ and compare \xmg\ to other existing grammar specification frameworks for tree-based grammars

Three reasons to adopt TAG-based surface realisation

Surface realisation from flat semantic formulae is known to be exponential in the length of the input. In this paper, we argue that TAG naturally supports the integration of three main ways of reducing complexity: polarity filtering, delayed adjunction and empty semantic items elimination. We support these claims by presenting some preliminary results of the TAG-based surface realiser

GenI, un réalisateur basé sur une grammaire réversible

National audienceEn génération, un réalisateur de surface a pour fonction de produire, à partir d'une représentation conceptuelle donnée, une phrase grammaticale. Les réalisateur existants soit utilisent une grammaire réversible et des méthodes statistiques pour déterminer parmi l'ensemble des sorties produites la plus plausible; soit utilisent des grammaires spécialisées pour la génération et des méthodes symboliques pour déterminer la paraphrase la plus appropriée à un contexte de génération donné. Dans cet article, nous présentons GenI, un réalisateur de surface basé sur une grammaire d'arbres adjoints pour le français qui réconcilie les deux approches en combinant une grammaire réversible avec une sélection symbolique des paraphrases

A Symbolic Approach to Near-Deterministic Surface Realisation using Tree Adjoining Grammar

International audienceSurface realisers divide into those used in generation (NLG geared realisers) and those mirroring the parsing process (Reversible realisers). While the first rely on grammars not easily usable for parsing, it is unclear how the second type of realisers could be parameterised to yield from among the set of possible paraphrases, the paraphrase appropriate to a given generation context. In this paper, we present a surface realiser which combines a reversible grammar (used for parsing and doing semantic construction) with a symbolic means of selecting paraphrases

Russian verbal prefixation: A frame semantic analysis

This book addresses the complexity of Russian verbal prefixation system that has been extensively studied but yet not explained. Traditionally, different meanings have been investigated and listed in the dictionaries and grammars and more recently linguists attempted to unify various prefix usages under more general descriptions. The existent semantic approaches, however, do not aim to use semantic representations in order to account for the problems of prefix stacking and aspect determination. This task has been so far undertaken by syntactic approaches to prefixation, that divide verbal prefixes in classes and limit complex verb formation by restricting structural positions available for the members of each class. I show that these approaches have two major drawbacks: the implicit prediction of the non-existence of complex biaspectual verbs and the absence of uniformly accepted formal criteria for the underlying prefix classification. In this book the reader can find an implementable formal semantic approach to prefixation that covers five prefixes: za-, na-, po-, pere-, and do-. It is shown how to predict the existence, semantics, and aspect of a given complex verb with the help of the combination of an LTAG and frame semantics. The task of identifying the possible affix combinations is distributed between three modules: syntax, which is kept simple (only basic structural assumptions), frame semantics, which ensures that the constraints are respected, and pragmatics, which rules out some prefixed verbs and restricts the range of available interpretations. For the purpose of the evaluation of the theory, an implementation of the proposed analysis for a grammar fragment using a metagrammar description is provided. It is shown that the proposed analysis delivers more accurate and complete predictions with respect to the existence of complex verbs than the most precise syntactic account

Construction of a formal grammar of Serbian using a metagrammar

Ovaj rad predstavlja proces izrade osnova FBLTAG gramatike srpskog jezika, a zatim i proces izrade njene metagramatike, čija primena na osnovne modele rečenica u srpskom jeziku omogućava njihovu automatsku sintaksičku analizu. Prvo pogavlje rada daje uvod u polje obrade prirodnih jezika, navodeći istorijat discipline i njene podgrane. Veća pažnja posvećuje se automatskoj obradi srpskog jezika, gde se daje pregled dosad ostvarenih rezultata, počevši od analize fonetike i fonologije, pa sve do analize sintakse. Za svaku od navedenih sfera navode se i konkretni alati i resursi koji su dosad razvijeni za srpski jezik. Drugo poglavlje donosi pregled pojma formalna gramatika, da bi se zatim usmerilo na oblast unifikacionih gramatika kao modela koji čini okvir ovog rada. U nastavku se detaljno iznosi struktura unifikacione gramatike koja će u nastavku rada biti primenjena na srpski jezik ‒ FBLTAG. U drugom delu poglavlja uvodi se pojam metagramatike, kao i konkretne metagramatike koja se u ovom radu koristi za sažeto predstavljanje gramatike FBLTAG ‒ XMG. XMG se obrađuje detaljno, pri čemu se opisuje njegova struktura, namena i princip funkcionisanja, kao i perspektive za primenu na srpski jezik...This paper presents the process of creating the basis of FBLTAG grammar of the Serbian language, followed by the process of building its metagrammar, whose application on basic sentence models of Serbian allows for their automatic syntactic analysis. The first chapter of the thesis gives an introduction to the field of natural language processing by outlining the history of the discipline and its subfields. The chapter focuses on automatic processing of the Serbian language, providing an overview of the results achieved so far, spanning from the analysis of phonetics and phonology to parsing. Tools and resources that have been developed for the Serbian language are listed for each of the stated fields. The second chapter offers an overview of the concept of formal grammar, only to focus on the area of unification grammars as a framework for the thesis. The structure of the unification grammar that will later be applied to Serbian ‒ FBLTAG ‒ is presented in detail. The second part of the chapter introduces the concept of metagrammar, as well as the specific metagrammar ‒ XMG ‒ used in the thesis in order to describe FBLTAG in an abstract way. XMG is presented in detail, through describing its structure, purpose and its principles, as well as prospects for its use on the Serbian language..